Allan, You might consider low ESR/ESL capacitors in parallel with the batteries to provide motor start surge. Much cheaper and require no maintenance.
See ya! Marv Director of Technology and Support, North America SolarEdge Technologies, Inc. Tech Support North America: +877.360.5292 Mobile: +530.392.0356 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Allan Sindelar Sent: Wednesday, February 15, 2012 9:53 AM To: RE-wrenches Subject: [RE-wrenches] Design Question re Battery Bank Sizing Esteemed fellow Wrenches, We need to size a battery bank for a GTWB just for starting a well pump. The well is on its own meter, so as long as the battery voltage does not crash when the pump starts there will be plenty of capacity left over for minimal loads. We'll be using sealed batteries, most likely Concorde SunXtenders. According to theSunXtender Technical Manual, Concordes can handle up to a C/0.2 charge rate (500A for a 100Ah battery), but there is no discussion of maximum discharge rates or voltage drop due to large surge loads. The pump is 3HP and is conventional 3-wire, not soft-start. The well is 940ft. and the depth to water is unknown. It pumps into a pressure tank, not open discharge. Customers are not interested in replacing the pump, but might be talked into adding a soft start Franklin controller, although at this preliminary design stage we're not certain one is available for this particular model. The inverter would be a Radian, so system voltage is 48V. I would think that configuration would make a difference, as well as size. Using 12V batteries in series/parallel would minimize interconnect and terminal resistance. I think that it would also allow multiple paths for discharge current, reducing the voltage dip. What's your best guess at the smallest size battery bank that would reliably start this pump, and how would it best be configured? Thank you, Allan Allan Sindelar al...@positiveenergysolar.com<mailto:al...@positiveenergysolar.com> NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com<http://www.positiveenergysolar.com/> ************************************************************************************ This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses. ************************************************************************************ CONFIDENTIALITY NOTICE: This e-mail and its attachments are intended only for the use of the individual or entity who is the intended recipient and may contain information that is privileged, confidential and exempt from disclosure or any type of use under applicable law. If the reader of this e-mail is not the intended recipient, or the employee, agent, or representative responsible for delivering the e-mail to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this e-mail is strictly prohibited. If you have received this e-mail in error, please reply immediately to the sender. P Please think of the environment before printing this email ************************************************************************************ This footnote confirms that this email message has been scanned by PineApp Mail-SeCure for the presence of malicious code, vandals & computer viruses. ************************************************************************************
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